A semiconductor memory device includes a redundant memory which stores a predetermined information instead of a main memory when a memory cell of the main memory is disabled, and a redundant decoder circuit supplies an active signal to the redundant memory in accordance with an address signal.
A conventional redundant decoder circuit includes a plurality of fuses which are cut to correspond to a content of the address signal. In this redundant decoder circuit, when an address signal corresponding to a normal memory cell of the main memory is applied to the redundant decoder circuit, no signal is applied to the redundant memory in accordance with the address signal, so that the redundant memory becomes inactive state. On the other hand, when an address signal corresponding to a disabled memory cell of the main memory is applied to the redundant decoder circuit, an active signal is applied to the redundant memory to activate a predetermined redundant memory cell.
According to the conventional redundant decoder circuit, however, there is a disadvantage in that if a redundant memory cell selected by the redundant decoder circuit is disabled, a semiconductor memory circuit is not used as a whole, even if there a normal redundant memory cell is available in the redundant memory. As a result, the semiconductor memory device must be replaced by another one to lower a fabricating yield.